Field of the Invention
The present invention relates to an inspection apparatus, exemplified by an ophthalmologic apparatus configured to inspect a fundus or an anterior segment of an eye to be inspected. The present invention relates to an apparatus in which a plurality of optical systems are arranged with use of beam splitters and which is configured to perform fundus photography and anterior segment photography, and more particularly, to an apparatus having a function of cancelling and correcting aberration of an eyeball of a subject to image a minute portion of a fundus with high magnification and high resolution.
Description of the Related Art
In recent years, a scanning laser ophthalmoscope (SLO) apparatus configured to two-dimensionally irradiate a fundus with laser light, receive light reflected from the fundus, and convert the received light into an image is known as an ophthalmologic image pickup apparatus that is one type of inspection apparatus. In particular, investigations have been made on an AO-SLO having an adaptive optics (AO) function for measuring aberration of the eye to correct the aberration when the fundus is imaged with high magnification. In this type of apparatus, a plurality of optical systems are arranged, such as a low-magnification wide-angle optical system configured to image the fundus with a wide angle of view, an AO optical system having the adaptive optics function and configured to image the fundus with high magnification and high resolution, an anterior segment optical system configured to image an anterior segment, and a fixation lamp indication optical system configured to change a fundus imaging range of the AO optical system. Optical paths of those optical systems are separated from one another as follows. Beam splitters, such as half mirrors and dichroic mirrors, are arranged so as to be eccentrically tilted, and the optical paths are separated from one another in a transmitting direction and in a reflecting direction.
In Japanese Patent Application Laid-Open No. 2007-296209, there is disclosed an AO-SLO apparatus in which optical paths are separated by beam splitters eccentrically tilted. This apparatus includes a plurality of beam splitters or dichroic mirrors. Note that, “eccentrically tilted” refers to the state in which an optical element such as a beam splitter is eccentrically arranged so that an optical axis thereof is tilted or rotated with respect to an optical axis of illumination light or the like. For example, one beam splitter separates a high-magnification fundus illumination system or a low-magnification fundus illumination system, which is configured to project illumination light to the fundus, from other optical systems. Further, another beam splitter separates a fixation indication optical system and an anterior segment observation optical system from other optical systems. A dichroic mirror separates a wavefront image sensor optical system, which is configured to measure aberration of the eye, from other optical systems. In Japanese Patent Application Laid-Open No. 2007-296209, there is also disclosed an aperture beam splitter configured to separate the low-magnification fundus imaging optical system and the high-magnification fundus imaging optical system from each other.
In an ophthalmologic apparatus such as the AO-SLO apparatus in which the plurality of optical systems are arranged as described above, the optical paths are separated by the eccentrically-tilted beam splitters as disclosed in Japanese Patent Application Laid-Open No. 2007-296209. However, those beam splitters are eccentrically tilted in the same plane (in the same drawing sheet), and hence axial astigmatism remains. Thus, for example, a problem such as distortion in an obtained image arises, and optical performance satisfactory for an image pickup apparatus cannot be obtained.